the Greenfield Frames forum has some requests for description and pics of an overhaul of a Greenfield newer-style transmission – the one mounted above the chassis frames to the left side of the frame, with a short transmission shaft. I’m no expert in Greenfield but from what I can see on the forum this type of transmission seems to be common to many of the later models. I have just undertaken an overhaul of mine and offer a description of the process and several of the gotchas. My mower is a Greenfield FastCut 30, bought second hand several years ago, with only 93 hours showing on the clock.
I am in the southern highlands of NSW and so routinely mow large amounts of relatively dry grass, which generates lots of floating frass which gets everywhere. I am not a mower or engineering professional, but I’m comfortable around machines and tools and am prepared to have a go.
Anyway, the reason for overhauling the transmission was that I was getting OK drive traction going both backwards and forwards, but after an hour of hard work the transmission would start to stick in forwards or reverse or, dangerously, both at the same time. The former had me heading into obstructions and the latter threatened burnout, requiring the engine being turned off to unload the stuck clutch wheels.
Other posts here have emphasised that the clutch linkage from pedal to transmission is prone to being clagged with grass, and that was certainly the situation for my mower when the problem first started to appear. Anyway, I found and fixed that problem to the extent that clutch linkage travel was still quite free while the traction problems got worse, leaving the clutches in the transmission as the likely culprit. In particular, there seemed to be little spring resistance in the interior driven plates so it was possible that the springs had broken. As reported elsewhere in the forum, broken clutch springs are rare but not unknown.
Unfortunately the worsening of the problem coincided with the sale of Greenfield to Cox, so getting hands on the likely needed parts was delayed until last month, when I finally got around to having a go at it.
Removal of the clutch required the following: • Remove the rear cover, • Get the drive belt out of the way, • Disconnect the clutch yoke, • Disconnect the drive chain, • Disconnect the cutter deck counterbalance spring, and • unbolt the outer bearing carriers
Removal of the transmission started with removing the rear cover (seat etc) and battery (a safety factor but mostly for ease of access).
Next step was to release the drive belt from the V pulley, which necessitated disengaging the small leaf spring plate from the notch bar by poking a screwdriver in the neatly positioned hole in the V-pulley plate, then using a spring hook tool to remove the spring from the end of the carrier bar. The Greenfield diagram shows the idea.
Not having a Greenfield spring hook tool I crafted one out of fencing wire – it worked well enough. Disconnect the spring from the end of the carrier bar and remove the spring anchor to simplify access. The spring will probably fall off the pulley mount but that’s OK because it’s easy to put back on. Push the belt pulley backwards to release the drive belt and take the drive belt loop out of the way; out the back of the mower is OK.
Disconnecting the clutch yoke bar only requires removal of the circlips connecting it to the clutch links. Access is reasonable and a screwdriver will prize the circlips off, just don’t let them get away . It is not necessary to disassemble the yoke bar at this stage. Removal is facilitated by loosening the bolt holding the rear clutch link guide to the frame tray, and rotating it out from around the rear clutch link. This may not be necessary, and doing the bolt back up again involves grovelling upside down to get to the well-hidden nut under the tray.
Disconnecting the drive chain without finding the joining link involves first undoing the bolt holding the disk chain guard washer onto the end of the transmission shaft. On my mower the bolt showed the remains of a medium strength thread locker, so that was used for reassembly. Loosen the chain tensioner bolted to the side of the frame in front of the clutch sprocket and get it as far forwards as possible using the adjuster bolts at the front of the tensioner plate. This gives enough slack in the drive chain to unhook it from the large sprocket on the axle; you can then push the mower backwards to run the unhooked chain around the large sprocket, after which it can be disconnected from the small drive sprocket on the transmission. This was a slightly difficult process because the chain did not have much space between the large sprocket and the tyre, and it got quite tight near the end of rotation. It might have been better to unhook the chain from the front of the large sprocket and push the mower forwards – don’t know.
The cutter deck counterbalance spring runs alongside the wheel side of the transmission and has to be removed to give enough room for the transmission to be lifted out. Bring the cutter up to its maximum height to unload the spring as much as possible. Get a 14mm socket and ratchet driver onto the nut at the back of the frame because it’s got lots of turns before it lets go. Pull the shaft out and move the counterbalance spring/shaft away from the transmission.
The transmission is held into the mower frame by two sets of bearing plates, one set on each side of the transmission clutch pulleys. The bolts holding the bearing plates onto the sprocket-side frame have plenty of space and are easy to remove. The bearing plates on the battery side are a different matter. The heads of the bolts have very little clearance to the hub of the clutch pulley on the battery side, and can only be removed from the frame by use of a cut out milled into the hub of the pulley on the battery side. On my mower this cut out is not present on the other clutch pulley on the sprocket side of the transmission, which did eventually become a gotcha. Even with the cut out there is little space to wrangle the bolt out, but it is possible (and necessary).
Having done this once it would only take 30 minutes or so to get the transmission out of the mower again.
Disassembly involves pulling the transmission apart from the outside in: • Remove the sprocket • Remove the shaft bearings • Remove the clutch pulleys • Record the disposition of the shims • Remove the inner clutch plates and yoke bar/bearing.
In my case removing the sprocket was quite a trial. Even though the sprocket itself was slightly free on the shaft, the woodruff key was a press fit in the key slot of the socket such that a large puller was necessary to hoik the sprocket off the shaft over the resistance of the key. I did try using the adjacent bearing plate for that purpose (as advised elsewhere in the forum) but only succeeded in bending the plate . Applying sufficient force via a bearing puller eventually did the trick but it took some doing.
After I got it apart I took the liberty of grinding down the sides of the woodruff key slightly so that it would only require mild force to remove next time. I also noted that the woodruff key has embossed in it a pattern from the thread of the screw that holds the sprocket and disk chain guard washer in place. That means that if the woodruff key does need to be replaced (not highly likely) then it may be necessary to use a thread cutter to enable the bolt to go back into the shaft. So, don’t lose the original sprocket woodruff key.
The bearings have an unusual configuration in that their inner races are extended to provide for retaining grub screws. Removing the shaft bearings was a simple matter of loosening the grub screws and using a small puller to overcome the slight resistance, most from minor corrosion on the shaft. I did carefully note the distance of both bearings from their respective ends but ultimately it did not matter because both of the bearings get put back on to the shaft as far as they will go and are set once reinstalled.
With the sprocket now removable, it was returned to the shaft and used as both a mount and rotation preventer for getting the large nuts holding the outer clutch pulley bearings onto the shaft. The transmission was held (carefully) by the socket in a vice to make the whole assembly amenable to handling. This enabled the large clutch pulley bolts to be undone with a large shifter. These large nuts had also been secured with a medium strength thread locker.
Behind each of the clutch pulleys is one large washer and none-to-several smaller shims and the springs – the subject of much debate elsewhere in the forum. Note how many shims were installed in each side; in my case, 3 and none. Despite my expectations the springs were intact.
With the large outer clutch plates, washers, shims and springs removed it is a simple matter to slide the inner clutch plates and yoke bearing off the squared section of the shaft. Even though the fit of the cork-on-aluminium clutch surface is not particularly precise, it is probably a good practice to ensure that the clutch pulleys and inner plates remain identified as pairs for re-installation together.
With everything as removable as it should be it should only take 15 mins to disassemble the transmission.
Rectifications involved checking and restoring the condition of: • the outer clutch pulleys, • the inner clutch plates, • the central drive shaft, and • the yoke bearing.
With the transmission apart it was obvious what the problem was – it had been badly gummed up by a lubricant. Someone had applied a generous amount of a molybdenum grease to the square shaft and that had subsequently been flung out and saturated the cork linings. As noted elsewhere in the forum, only dry lubricants should be used in this type of transmission to avoid the inevitable dust and dirt turning the grease into valve grinding paste and from flung grease contaminating the cork linings.
The clutch rubbing surfaces on both outer clutch pulleys were in good condition and so the pulleys only required cleaning.
The inner clutch plates needed a lot of work. I didn’t have spare cork linings and the ones in there had plenty of meat left so I decided to take a punt on cleaning them. Half an hour of rubbing the plates with paper kitchen towels soaked in methylated spirits did a good job of getting a lot of the grease out of the cork linings such that they are now more tan than grey and have the grabbiness you would expect from nearly fresh cork.
The only unknown here is whether the metho affected the adhesive of the cork linings. The cork linings were still tightly glued to their backing but I did notice some delamination around the outer edges, which I fixed with localised injections of solvent based quick grip using the wet bond method. While this was drying the two clutch plates were pressed together using a vice and clamps. Hopefully the glues will still be OK despite the metho and grease – time will tell.
The other matter for the inner clutch plates is wear on bearing surfaces of the square hole through the middle. With all of the old grease removed from both the square holes and square shaft, it was possible to check the quality of the fit of the plates on the shaft. The reverse drive plate (sprocket side) was a close and smooth fit on the shaft, but the forward drive plate had some play and did tend to stick on the shaft, probably responsible for much of the original drive problem. Fine abrasive paper (120 grade) was used carefully to smooth of the square bore of the sticking clutch plate.
The square shaft itself cleaned up nicely. There was one area of corrosion which probably contributed to the plate sticking – a light buffing with the fine abrasive paper was used to take the corrosion back to the surface of the shaft. Use of abrasives was minimised because the last thing I wanted to do was to increase the play between plate and shaft.
The yoke bearing needed little attention, just removal of the excess grease. Because the yoke bearing was OK, smooth and free, I didn’t have to disassemble the yoke bar.
The largest time consumer here was getting the grease out of the cork linings. Without that, cleaning and buffing the components would only take 30 mins or so.
Assembly consisted of: • lubrication of the cleaned shaft and other inner components • placement of springs, washers and shims on the sprocket side before bolting that clutch pulley on, • ditto with the battery side • replacement of the shaft bearings, and • replacement of the sprocket.
I used powered graphite as the lubricant for the cleaned up square shaft and inner plates. It has been mentioned elsewhere in the forum, as well as spray on silicone dry lubricants. In the past I’ve had better results with carbon over the spray ons, and I think it is possible to apply more and have it last longer. It is messy but being generous won’t cause a problem. A nickel anti-sieze compound had also been recommended but the version of that I got was somewhat gritty and not smooth like a lubricant, so it wasn’t suitable. After lubrication with plenty of smoothed-on graphite, both inner plates and the yoke bearing were suitably free on the square shaft.
Next were the washers, springs and shims. Having read posts in this forum, their adjustment appears to be a dark art. Having looked at the mechanism I think that it’s quite clear. Starting from the outside in, the large nut holding an outer clutch pulley onto the shaft bears on the inner race of the clutch pulley bearing, which in turn bears on the shims and a washer, which butt up against the sharp shoulder of the inner square section of the centre shaft. Same for the other side. I think that any shims that are used should be installed between the bearing and the washer, not between the washer and the shaft, because the shims are not strong enough to resist deformation if the outer pulley bolt is done up extra hard – one of the shims that I removed had been so distorted. The inner plates and yoke bearing form a constant-width assembly that is centred in the gap between the outer clutch pulleys by the spring on each side of the inner assembly. The springs rotate with the square shaft between the hubs of the inner plates and the washers of the outer pulleys. The gap between the large outer pulleys is set by the width of the square section of the shaft, the thickness of the washers and the thickness of any added shims. Because my problem was with binding of the plates I added shims to ensure that I had plenty of clearance between the cork linings and the outer pulleys. I added the same amount of shims to each side, mostly to establish a baseline for behaviour of the transmission once assembled again.
It is apparent from looking at the transmission that the only things that the shims can do is increase (by adding shims) or decrease (by removing) the gap between the two outer clutch pulleys, which similarly increases or decreases the pedal travel before engagement of either clutch. As the cork pads wear, the only way of compensating is to disassemble the transmission to remove a corresponding number of shims. Biasing the shim stack to one side or the other is the only way of moving the pedal neutral position, which is a major design oversight IMHO. If I get tired of pushing the pedal too far forwards and backwards then I might pull it out again and remove the shims on the reverse (sprocket) side to reset the pedal position a bit more forward.
Getting it all together is reasonably easily done by assembling the reverse (sprocket) side first. Put the washer and shims for the sprocket side clutch pulley onto the shaft followed by the pulley and nut, done up only hand tight at this stage. *** GOTCHA WARNING – the clutch pulley used at the sprocket end as to be the one WITHOUT the cut out for the bolt head at the hub, because the one WITH the cut out HAS to go onto the Battery end of the shaft.*** If you get it wrong you have to pull it apart again to swap them around – did that . Put the drive sprocket back onto the transmission shaft (remember its now a firm but not hard fit) and use that to mount the transmission upright in a vice again. With the interior part of the shaft now sitting up, install the spring and mating inner plate for the reverse side, then yoke bar with bearing, other inner plate, spring, large washer and shims, other clutch pulley (again, the one with the bolt cut out at the hub) and other large nut in sequence onto the shaft. Note that the springs will hold the upper clutch pulley above the height of the thread of the upper large nut, so press the upper clutch pulley down a bit to get the nut started.
It was now necessary to add the thread locker to the large clutch pulley nuts before doing them up snugly. At my workbench it was possible to turn the assembly 90 degrees such that the shaft was horizontal whilst still prevented from rotating. I was then able to compress each clutch pulley enough to reveal the nut shaft thread so I could apply a blob of medium strength thread locker (Loctite 243) before doing up the nut firmly, not hard, no more than 20 ft.lbs I estimate.
With the clutch plate/pulley assembly now bolted together on the shaft, the shaft bearings were then installed, with the inner bearing plates between each shaft bearing and pulley. As mentioned above I did carefully record the distances from inner race to end of shaft, but upon installation it transpired that they simply need to be pushed on as far as they can go. The Greenfield guys apparently got everything sized just so. *** GOTCHA WARNING: The extended inner races of the shaft bearing have different orientations– the battery side has the grub screws towards the battery while the sprocket side has the grub screws away from the sprocket. Not hard to fix but annoying if you get it wrong. *** Leave doing up the grub screws until the transmission has been mounted back in the mower frame.
Installing the sprocket was now a simple matter. Make sure that the second bearing plate for the sprocket end bearing is put in place before the sprocket itself is installed. The nickel anti-seize originally intended for the inner shaft was now used to ensure that the sprocket stayed removable. The chain guard washer and retaining bolt could be installed at this point, but I left them off to facilitate re-installation of the drive chain by the wind-on method.
Installation was, as they say, the reverse of installation, requiring: • installation of the bearing plates to the frame, • installation of the drive belt, • attachment of the yoke bar to the clutch links, • reattachment of the cutter deck counterbalance spring, • Installation of the drive chain, and • Installation of the Battery and Cover.
The transmission is attached to the mower by bolting the bearing plates to their mounts on each side of the transmission hole in the frame. The assembled transmission is something of a tight fit, but it should be able to be pressed in place by hand. Try to get the drive belts snugged into the clutch pulleys as they go in – it’s easier than doing them afterwards; lining the belts up a bit before lowering the transmission in helps. *** GOTCHA WARNING – the yoke bar in the centre of the transmission has to be above both the forward and rearward edges of the frame hole for the transmission – the yoke bar is just long enough to get stuck under one of the other and can’t be rotated out from underneath without disassembling the yoke bar or taking the transmission out again. *** Did that . Make sure that the bearing plates are both inside of the mower frame such that the bearings are firmly held. The bearing plate bolts are designed to be installed from inside to out – the square hole keys for the cup head bolts are on the bearing plates. Reinstalling the bearing retainer bolts in the sprocket side is easy – plenty of room. Reinstalling the bolts on the battery side is a pain, involving careful alignment of the bolt head notch in the clutch pulley, a magnetic holder and a non-magnetic poker (ie a stick) and lots of persistence and wiggling. Somebody didn’t think that one through well.
The drive belt loop is retrieved from out the back of the mower and guided back over the clutch pulleys and around the front V pulley. Push the V pulley forwards to simplify re-installation of the drive tension spring. Remove the screwdriver from the notch release hole if it’s still there : ) Put the spring anchor back onto the end of the notched bar and the front end of the drive tension sprint spring back into the pulley mount. Then, approaching the assembly from the rear of the mower, use your spring hook to pull the spring backwards and onto the spring anchor. Give the notch bar or V pulley a push forwards to ensure that the notch bar leaf spring can slot into the most forward notch.
Assuming that you’ve avoided the yoke bar gotcha above, reattaching the yoke bar to the clutch links is a simple matter of reinstalling the two circlips front and back. If the rear clutch link guide was rotated out of the way, look forward to getting down and dirty to get the non-captured nut tightened again after rotating the guide back into position.
Reattaching the cutter deck counterbalance spring really needs three hands – one on the hook to pull the spring out far enough to get the bolt end through the frame, one to put the washer back on the shaft and stop it from falling off and one put the nut on a first few threads. This probably could be simplified, I didn’t find a way. The nut is done up all the way; about 3cm worth so have a 14mm socket and ratchet driver handy.
Installing the drive chain involves fishing it out from the gap between the wheel and large sprocket, looping it over the small transmission sprocket and starting it onto the large axle sprocket. Not having the chain guard washer in place here helps. Push the mower backwards again to have the chain feed on to the correct path on the big sprocket, but watch that the chain doesn’t simply fall off the bottom of the big sprocket as it goes around. It should fit all the way round the big sprocket without too much hassle.
Once the drive chain is in place, move the tensioner backwards onto the chain until there is only a small amount of play in the chain between the small sprocket and the top rear of the large sprocket. Greenfield recommends 3mm, I gave it about 5, which was still substantially less than what it was when I pulled it apart. Do up the adjuster nuts and lock nuts firmly. Reinstall the chain guard washer to the drive sprocket, using a bit of medium strength thread locker for the retaining bolt. Some care is needed to ensure that the small bulge pressed into the chain guard washer fits neatly into the end of the sprocket key hole, keeping everything aligned.
In the end the cause of this drive problem was that which was considered most likely – the clutches in the transmission were clagged up by unnecessary, inappropriate and excessive lubrication. The sad thing was, someone would have to have pulled it apart to do that in the first place.
I have only had a chance to run the mower briefly since this overhaul but I am glad to report that it is working much better – the transmission is responsive and progressive and shows no sign of sticking. The pedal travel is longer than it could be but I’m OK with that for the moment.
Once it rains and we get some grass I’ll give it a solid go and see if the clutch lining glue holds up to hard work.
Well, the overhaul to the transmission worked for a while but then after a years occasional use the same old symptoms started to show - sticking in forward and sometimes reverse as well. I had a couple of other things to fix on the mower so I got back into the transmission and had a look.
I had taken a shortcut in the previous overhaul to try to keep the original cork linings, and had rubbed them with metho to get the grease out of them. Turns out that process wasn't thorough enough - the corks ended up with grease on their surfaces again which I assume came from the heat of some hard work mobilised the remaining soaked-in grease, which then transferred to the matching clutch pulley surfaces. The extra slip made me push harder on the clutch pedal to get motion and that higher force contributed to jamming the clutch plate (inner disk with cork) up against its mating clutch pulley (outer disk with the belt). See pic of contaminated surfaces attached.
Since last fix I'd managed to get some replacement corks so I was able to strip off the old corks, clean everything thoroughly and put the new corks on. The old corks mostly just flaked off using a broad scraper and I used paint thinner to get rid of the remaining bits of old glue. One of the pics below shows a cross section of the old cork - the majority of the cork still appears to be OK, so possibly just sanding off the top surface of the old cork might have been OK if I didn't have replacement corks on hand. Interestingly, the old cork pads were thicker than the new ones (3.2 mm for the old vs 3 mm for the new) but that might just have been down to remnants of the glue lining on the old corks.
I was surprised to find that remnant grease in the yoke bar bearing had managed to get back onto the square shaft and gum up the carbon film lube surface there. So, the grease was cleaned away again and the sliding surfaces refreshed, rubbing carbon powder onto the square shaft and the matching square holes of the clutch plates.
With the new corks in place the feel of the clutches is better, with more progressive engagement and no sticking.
Another problem with the original fix was that I'd reassembled the transmission with lots of clearance (extra shims between washers and clutch pulley plates) to ensure that it worked without drag. This had the undesirable effect of both putting the clutch pedal neutral position too far back (hard to press for reverse) and with an unnecessary amount of play. Solution here was to leave out most of the shims and leave just one on the forward clutch (battery side). Even though the clutch pulleys do rub slightly on the clutch plates (the path of the drive belt actually pulls them off line slightly), the pedal play is now OK and it has a better neutral position.
After all of the palava of the original transmission overhaul, this removal, fix and reinstallation took less than a day. The mechanical work went quickly - most of the time was spent waiting for the cork glue to dry.
Other simplifications to the process this time were that the sprocket and shaft bearings came off easily and I managed to find the removable link to the drive chain so that its removal and reinstallation was much simpler.
Just for the sake of clarity, the model of this mower appears to be an Evolution 3 Mk2A 12.5-30 - see decal pics. It's a bit hard to tell because not all of the linkages are as described in the manual and the mechanism for the hand brake isn't a match for any of the manuals.
Well, despite all the care the old sticking problem resurfaced after another year. A 1cm strip of corrosion on the square shaft seems to have been a focus for collecting gunk and even though it was almost imperceptible, it could have been enough to stick into the matching aluminium face of the driven clutch plate. Also, it seemed that the outer pulleys were showing play at the limit of their tolerance (5mm total side to side at the rim, an informal limit discussed in other threads) and so I took the plunge to replace nearly everything - square shaft, inner plates, outer pulley and springs (see pic). I retained only the outer transmission mount bearings (relatively new) and the shims. Expensive, but cheaper than a new mower.
Net result, works well again. Two factors that might have helped this time around:
The new driven plates have extended bosses that meet at the centre of the transmission. Apart from giving increased contact area on the square shaft (which reduces friction loads) the driven plates now sit inside the yoke bearing with a slight interference. On my original transmission the centre of the yoke bearing was filled with an aluminum spacer which I had to remove - a single cut with a hacksaw was sufficient. This is a significant improvement because the yoke bearing can now help to pull the driven plate back off the clutch pulley, helping to overcome the stick problem.
I found that on assembly of the new components and tightening the clutch pulley nuts that the clutch pulleys were not trued to the centre shaft. This could be seen by sitting the transmission up on a vice and watching the outer edges of the clutch pulleys as the square shaft was rotated. The out of true shows as the rim of the clutch plates moving back and forth a couple of milimetres as the square shaft is rotated. Given that there is only a couple of milimetres in the clutch contact travel, this could make a significant difference to the clutch engagement process. I corrected the wobble of one clutch pulley by giving it a calibrated (light!) tap with a rubber mallet. Unfortunately I was in a rush to finish and didn't do both (kicking myself now) because there is a slight pulsing engagement at near neutral which means that the other plate is not riding true either. If I pull it out again I'll pay a lot more attention to truing up the clutch pulleys to the square shaft.
Hopefully this fix will be enduring so that I won't have to provide yet another update.
. It is not necessary to disassemble the yoke bar at this stage. Removal is facilitated by loosening the bolt holding the rear clutch link guide to the frame tray, and rotating it out from around the rear clutch link. This may not be necessary, and doing the bolt back up again involves grovelling upside down to get to the well-hidden nut under the tray. 
. Applying sufficient force via a bearing puller eventually did the trick but it took some doing.
. Make sure that the bearing plates are both inside of the mower frame such that the bearings are firmly held. The bearing plate bolts are designed to be installed from inside to out – the square hole keys for the cup head bolts are on the bearing plates. Reinstalling the bearing retainer bolts in the sprocket side is easy – plenty of room. Reinstalling the bolts on the battery side is a pain, involving careful alignment of the bolt head notch in the clutch pulley, a magnetic holder and a non-magnetic poker (ie a stick) and lots of persistence and wiggling. Somebody didn’t think that one through well. 
